Problem: ${7 \div 0.4 = {?}}$
$ {7 \div 0.4 = 7 \div \dfrac{4}{10}} $ $ {\phantom{7 \div 0.4} = 7 \div \dfrac{2}{5}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {7 \div \dfrac{2}{5} = 7 \times \dfrac{5}{2}} $ $ {\phantom{7 \div \dfrac{2}{5}} = \dfrac{7 \times 5}{2}} $ $ {\phantom{7 \div \dfrac{2}{5}} = \dfrac{35}{2}} $ $ {\phantom{7 \div \dfrac{2}{5}} = 17.5} $